Shallow-Marine Carbonates - Trace Fossils as Indicators of Sedimentary Environments - page 690

rock. Early cementation is important and is aided by the chemical microenvi-
ronment around the burrows, resulting in the crystallization of calcite, celestite,
dolomite, goethite, or pyrite.
The name-bearer trace fossil of the Glossifungites Ichnofacies is now
regarded as a junior synonym of Rhizocorallium jenense ( Uchman et al.,
2000 ). Other characteristic trace fossils are Balanoglossites , Gastrochaenolites ,
Pholeus , Spongeliomorpha , and Thalassinoides . The former two ichnogenera
include both firmground burrows and borings, whereas other tracemakers are
capable of burrowing into soft and firm substrates to produce, for instance,
Chondrites , Palaeophycus , Siphonichnus , Lingulichnus , and Zoophycos .
A special expression of the Glossifungites Ichnofacies is a firm matground
substrate, resulting from the development of algal or microbial mats on the sedi-
ment surface. Such conditions are well known from Precambrian and Early
Cambrian units, but similar conditions repeatedly occur through the Phanero-
zoic. The related ichnofauna comprises surface traces of crawling and rasping
organisms, which benefit from the organic matter as mat scratchers and
digesters, mat stickers, or undermat miners ( Seilacher, 2007 ).
3.5 Trypanites Ichnofacies ( Frey and Seilacher, 1980 )
The substrate-controlled Glossifungites and Trypanites ichnofacies are inti-
mately associated, as the former has the potential to develop gradually into a
hardground of the latter ( Bromley, 1975 ). In contrast to the Glossifungites Ich-
nofacies, the Trypanites Ichnofacies is more restricted in its distribution to areas
with rapid cementation. Such conditions are common in subtidal and intertidal
environments, where this process may lead to an extensive pavement by hard-
grounds or beachrock, but the Trypanites Ichnofacies also occurs on rocky
shores or in reefs. Rapid lithification preferentially takes place in front of sand-
shoal complexes (including the shelf break), where the sediment is exposed to
wave sweeping and reworking.
Bromley and Asgaard (1993) proposed to replace or subdivide the Trypa-
nites Ichnofacies with the Entobia Ichnofacies for deep-tier borings with high
preservation potential and the Gnathichnus Ichnofacies including superficial
sculptures resulting from short-term bioerosion. However, Entobia and Gnath-
ichnus are probably better treated as ichnocoenoses within the Trypanites Ich-
nofacies ( MacEachern et al., 2007 ).
Hardgrounds are often well defined by a clear top surface colonized by epi-
benthic organisms (e.g., oysters, serpulid polychaetes) and mineral staining.
Bioerosion takes place on the hardground surface or from its top, marginal, or
undercut surface into the substrate. It comprises a variety of borings mainly pro-
duced by suspension-feeding organisms. Trypanites weisei from its type area in
the Middle Triassic of Germany occurs in micritic limestone assignable to the
Glossifungites Ichnofacies, where it superimposes a Balanoglossites ichnofabric
( Knaust, 2008 ). Its stratigraphical position, sedimentological and ichnological